The present invention relates to a slow scan stitching mechanism for an information transfer device and more particularly, but not exclusively, to such mechanisms for use in thermal ink jet printing and document scanning devices.
According to the present state of document scanning and printing technology, it is most cost effective to use a printhead (for example in thermal ink jet printing) having a width less than that of a full page. This means that scanning an entire document in one pass of the printhead is not possible and necessitates the butting of adjacent scan lines (known as stitching). Tolerances in the relative location of the butted scan lines is critical, and must be kept low in order to avoid objectionable defects in print quality.
Document scanning and printing devices are known in which the motion of the paper (or cartridge rail assembly motion) is used to achieve the above-mentioned precision stitching. The incrementing of the printhead in a particular direction (the slow scan direction) is done between successive printed swaths or scan lines, during which the paper is scanned in a perpendicular, fast scan direction. This successive incrementing is usually achieved by means of stepper motors, d.c. servomotors, or ratchet paw assemblies.
The primary problem with such architectures is a low print speed, due to the time required to increment the paper or guide rail assembly. Also, it is necessary to provide a separate drive mechanism for movement in both the slow scan and the fast scan directions, which adds to the mechanical and electrical complexity of scanning and printing devices.